1. Field of the Invention
The present invention relates to a pontoon system which acts as a floating support for watercraft. More particularly, the present invention relates to a pontoon system for lifting and supporting watercraft which stabilizes the watercraft during the lifting process by lifting the lighter (front) portion of the watercraft before lifting the heavier (rear) portion.
2. Description of the Prior Art
Reference is made to the following U.S. patents as typifying the structure of dry docks and pontoon systems for watercraft:
U.s. pat. No. Lehmann 3,448,712; and PA1 U.s. pat. No. Roberts 3,315,627.
The Roberts patent shows and describes a floating dry dock with both rigid and inflatable pontoons. Air is introduced into the various pontoons thereby creating lift. The pontoons extend the length of the dry dock structure without any intervening bulkheads. The water may be expelled from any particular pontoon by opening the valve between the compressed air supply and the pontoon.
The Lehmann patent shows and describes a dock using pontoons for use mainly as a towing apparatus. The pontoons have two chambers. One chamber is sealed and contains air. Water may be selectively expelled from the second chamber but the bow of the dock will remain above the surface of the water. These prior constructions did not allow for a controllable lifting of the bow of the watercraft before lifting the aft portion and did not utilize a chambered pontoon that allows water to be selectively expelled from all of the chambers. Because of the failure to lift the lighter (which is usually the bow) portion of the watercraft prior to lifting the heavier (which is usually the stern) portion of the watercraft, instability could result in a tipping over resulting in damage to the watercraft.